The invention relates to a brake for an open-end spinning rotor which is disposed by means of a shaft in a wedge-shaped gap of at least one pair of supporting disks. The brake has two mirror-symmetrically arranged double-armed tong arms, which can each be swivelled around an axle extending in parallel to the shaft, which carry brake linings at arms that can be applied to the shaft, and which, at the arms that face away from the shaft, can be spread apart by means of a common actuating element.
In a known brake of the initially mentioned type disclosed in commonly assigned U.S. Pat. No. 4,703,616, the actuating element is a bent leaf spring which is pressed in the direction toward the shaft and which deforms in the process and presses apart the arms of the tong arms which are connected with it. In order to ensure in this type of a brake without any high technical expenditures that the shaft of the spinning rotor is securely held in the wedge-shaped gap, it is also known from commonly assigned U.S. Pat. No. 4,706,450 to construct the brake shoes in such a manner, and/or arrange them relative to one another in such a manner, and/or actuate them in such a manner that the brake shoe, which during the braking moves in moving direction of the tangential belt, comes to rest against the shaft first.
In the case of a brake of a slightly different type disclosed in European Patent Application (EP-A) 0148,468, in which two tong levers are provided which are constructed as simple arms, these tong levers are held by means of a spreading element in an unbraked operating position and, by means of a spring, are changed to a braking position when the spreading element is moved away from the arms.
An object of the invention is to construct a brake of the initially mentioned type in such a manner that it is reliably ensured that the brake linings press against the shaft with equally high forces.
This object is achieved in that the actuating element is arranged to be freely movable in moving direction of the arms.
By means of this construction, it is ensured that the spreading forces are introduced into the tong arms by an equal amount, because these tong arms mutually support one another by means of the freely movable actuating element on the one side, and by means of the shaft, on the other side. The forces exercised on the shaft by the two brake linings are therefore always the same so that it is also possible to do without an asymmetrical arrangement and/or an asymmetrical actuating, and to apply the brake linings to the shaft simultaneously.
In a further development of preferred embodiments of the invention, it is provided that the arms of the tong arms facing away from the shaft are provided with sliding surfaces which enclose a preferably acute angle between one another and between which a spreading element can be inserted which is centered by the sliding surfaces. In order to ensure that the loading of the spreading element does not result in any varying introduction of force, it is further provided in an expedient development that the spreading element is supported by a loading element in such a manner that the direction of force from the loading element to the spreading element extends in the median line of the sliding surfaces.
In particularly advantageous embodiments of the invention, it is provided that the spreading element is a rotationally symmetrical body which is disposed opposite the sliding surfaces and the loading element at angular distances of 120.degree.. This development ensures that, also during an adjusting movement of the actuating devices, the relationships and directions of force remain the same.
In an advantageous embodiment of the invention, the actuating element is a cylindrical body. In a particularly simple manner, it is provided that the actuating element is disposed in a U-shaped guide which is formed by a swivelling lever, which can be swivelled around an axle which is in parallel to the axles of the tong arms, and which carries the loading element. This actuating element is basically inserted only loosely and is held in the respective required position by the loading element and the sliding surfaces.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.